As Andy says, follow the directions. They are usually on the back side of the label when you unwrap it. I just cooked one a month or so ago and it called for putting it "face" side down in a pan and heating at a pretty low temp. Glaze is totally optional but does give a nice flavor to the slices since it drips down into them. It isn't overpowering but you may have diet issues with it.

Another approach - place slices of bacon over the top of the ham for the first half of the cooking time - also this gives added flavour plus helps give the skin a nice crunch!!! The skin or cracklin is my favorite part of the ham!!!

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